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How to: Maintain a fifth wheel

As the chief fastener attaching tractor to trailer, a fifth wheel plays a fundamental role in the safety and maneuverability of combination vehicles. Unfortunately, this “alpha part” status often gets overlooked.

“I’d say that fifth wheels are probably one of the most neglected pieces on a truck,” says Eugene Brown, Fontaine’s technical services manager. Some truckers believe that as long as everything seems to be working well, maintenance is unnecessary, Brown says. “That thinking can come back to bite you.”

Brown often sees fifth wheels that clearly didn’t get the regular lubrication and inspection that manufacturers recommend. “A lot of guys don’t get much beyond the ‘tug test'” when hooking to a trailer, he says. “But that won’t tell you much, not even whether the lock is properly engaged.”

This apparent indifference among truckers is fostered by the products themselves, typically some of the most reliable and long-lasting metal on a truck.

“We’re getting about 600,000 miles from our fifth wheels,” says Mike Jensen, a mechanic at Caledonia Haulers in Caledonia, Minn. “If one gives us trouble before that, we’ll just throw a kit in it.”

Caledonia, a food-grade liquid bulk operation, runs 110 company trucks fitted with Holland fifth wheels. Each fifth wheel is inspected annually, as required by DOT regulations, but Jensen says that’s the extent of the service, other than greasing once a week.

Lubricant is the lifeblood of most fifth wheels on the market today. Without it, top plates become chafed and worn, jaw locks corrode and stop working, and steering gets difficult. All this leads to unsafe driving, especially on slippery roads.

Still, manufacturers constantly try to reduce or eliminate the need for fifth-wheel lube. Fontaine, Holland and Jost International, the three major suppliers of the North American Class 8 market, all sell premium models featuring maintenance-free bracket pins and top plates, mostly embedded with urethane pads that provide a slippery contact surface without grease or oil.

“Everybody is trying to minimize the number of lube points in their equipment,” says Marty Marsh, Midwest accounts manager for Jost. “This is important, not only for lowering maintenance costs, but also for avoiding the mess and environmental problems associated with excessive greasing.”

Fifth wheels have a long history of messy upkeep: While some people try to use as little grease as possible, others slather a thick layer across the top plate. The latter practice allows excess grease to fall onto the ground or the truck’s frame as soon as the rig backs under a trailer.

“It’s a huge problem,” says Mike Ginocchio, fifth wheel product manager at Holland. “There are between 1.5 million and 2 million tractor-trailers on the highways today. If some significant portion of them is dripping even a small amount of surplus grease onto roads and parking lots, that’s a lot of pollution over the course of a year.”

To help lessen this accumulating hazard, Holland in 2003 unveiled the industry’s first lubricant-free fifth wheel, aptly dubbed the NoLube. The product uses specially treated metals for the bracket pins and pockets, where the top plate attaches to the legs, kingpin jaws and locking mechanism, Ginocchio says.

Jost also is working to minimize grease waste, but is taking a slightly different approach, says Rich Carroll, vice president of sales and marketing. Jost is developing Lubetronic, based on a small lubricant cartridge fitted with an electric motor that is used in Europe. At set intervals, the device automatically delivers a tiny amount of grease to the fifth wheel’s jaws and locking mechanism. Those are the only parts “that will need to be coated to maximize their longevity,” Carroll says.

Still, most operators use standard models, requiring top plate grease once a week or every 3,000 miles – more with intense drop-and-hook uses – and jaw lubrication every 30,000 to 60,000 miles, depending on manufacturers’ recommendations.

Plenty of fifth wheel-specific lubricants are available, but high-quality chassis grease remains the most popular and economical product for top-plate lubrication, at least in regions where the ambient temperature remains above 0 degrees Fahrenheit. In colder conditions, heavy gear oil works better. Some truck owners use synthetic lubes, but Fontaine’s Brown says that can pose problems for truckers who regularly switch trailers.

“Unless you’re using the same grease for all your equipment, you could run into compatibility issues,” he says. Some mineral-based lubricants won’t mix well with synthetics, Brown says. “When that happens, the products degrade and form a gumlike substance that’s very tough to remove.”

Beyond lubrication, fifth wheels last longer if they’re not abused. Careless truckers have been known to squeeze their rigs under fully loaded trailers, then slam into the kingpin. Actions such as these accelerate wear and can damage tractor and trailer parts.

Longevity also is affected by application. Off-highway duty will dramatically trim life expectancy, as will construction work – particularly tip-trailer operations – and city work involving constant dropping and hooking.

Before fifth wheels wear out, though, they can be adjusted to tighten the slack that comes with use. When that fails to correct the problem, they can be rebuilt with kits.

The steps for rebuilding vary by brand, model and type of kit. Complete instructions are packaged with the kits and are normally available online at the manufacturers’ websites. None of these jobs is technically difficult, usually entailing fewer than a dozen parts. The biggest challenge for most people will be the removal of their fifth wheels, unwieldy slabs of iron weighing upward of 300 pounds. Jost models, though, can be rebuilt while attached to the truck.

The best way to avoid, or at least delay, the cost and effort of such tasks is with regular, thorough inspections and proper lubrication. Following are the recommended practices for ensuring maximum fifth wheel life.

THE JOB

CLEAN FIFTH WHEEL. Manufacturers recommend regular steam cleaning of the top plate, jaws and legs. Many owner-operators and fleets prefer simply to scrape off the accumulated globs of dirt and grease with a putty knife, brush and cleaning solvent.

INSPECT TOP PLATE. Examine the upper surface and outer edges, looking for damage, missing parts and excessive wear. Use a straight edge to determine the plate’s flatness. Shine a flashlight underneath and look for signs of grease seeping through cracks.

CHECK LOCKING MECHANISM. Inspect the jaw area, looking for damage, missing parts and excessive wear. Use a test pin, available from each manufacturer, to engage the locking mechanism. It should operate smoothly and fit tightly around the test pin. Using homemade test pins is not recommended. Make sure the release handle is secure and straight.

ADJUST LOCKING MECHANISM. Follow the manufacturer’s instructions when adjusting the locking mechanism of your fifth wheel. Regardless of brand, use the proper tool: a test pin, which will be exactly 2 inches in diameter and will fit squarely into the lock area.

INSPECT BRACKET PINS AND LEGS. Look for cracks and other damage. Make sure grease fittings, or zerks, are intact (where applicable) and free of blockage. Pins should show no signs of wear or slack. The top plate should tilt smoothly and freely.

INSPECT TRAILER BOLSTER PLATE AND KINGPIN. Use a carpenter’s square to determine the flatness of the bolster plate and the form of the kingpin. If either shows signs of deformity, replacement is necessary. Use a kingpin gauge to determine wear.

LUBRICATE JAW AND LOCKING MECHANISM. Unlike the top plate, these parts should be coated with a silicone-based spray lubricant or light oil.

LUBRICATE BRACKET PINS. Attach a grease gun to the bracket pin grease zerk. Ask a helper to pry up that side of the fifth wheel with a bar, allowing grease to fill the friction surfaces above the pin. Repeat on the opposite side.

LUBRICATE TOP PLATE. Apply high-quality grease to the rear portion of the top plate. This will be spread across the surface when a trailer is connected.

OPERATE WITH CARE. Use the truck’s air suspension to achieve the top level for backing under a trailer. Ideally, a trailer nose should make contact with the fifth wheel slightly behind the bracket pins, tipping the top plate flat during coupling. When dropping a trailer, crank the landing gear close to the ground, then dump the suspension air to reduce the weight on the fifth wheel before pulling away.